CZ305963B6 - Substrate with photocatalytic coating - Google Patents

Abstract

The present invention relates to a method for a cathode spray deposition of a coating with photocatalytic properties comprising titanium oxide at least partly crystallized in anatase form on a transparent or semi-transparent support substrate, such as glass, vitroceramic or plastic. The substrate is sprayed under a pressure of at least 2 Pa. The invention also relates to the resulting coated substrate, wherein said substrate constitutes the top layer of a series of thin antiglare layers.

Description

Carrier with photocatalytic coating

Field of technology

The invention relates generally to transparent or semi-transparent supports, in particular of glass, plastic or glass-ceramics, which are provided with a coating with photocatalytic properties which makes the supports non-dirty or, more precisely, self-cleaning.

An important application of these carriers concerns glasses, which can have very different uses, utility glasses used in household electrical appliances, vehicle glasses and glasses used in the construction industry.

The application of these glasses also applies to reflective glass of the mirror type (dwelling mirrors or vehicle rear-view mirrors) and to window-sill tinted windows.

The invention also similarly relates to non-transparent supports, such as ceramic supports or any other support which can be used in particular as an architectural material (metal, tiles ...). The invention preferably relates to substantially straight or slightly arched carriers, regardless of the nature of the carrier.

Prior art

Photocatalytic coatings have already been the subject of study, especially photocatalytic coatings based on titanium dioxide in the crystalline modification of anatase. Their ability to decompose dirt of organic origin or microorganisms in the presence of ultraviolet radiation is very interesting. These coatings are often hydrophilic in nature, which makes it possible to remove dirt of a mineral nature by spraying water or, in the case of external glass surfaces, by the action of rain.

This type of coating with non-soiling, bactericidal and algicidal properties has already been described, in particular in International Patent Document WO 97/10 186, which also describes several methods for obtaining such coatings.

The object of the invention is thus to improve coating techniques of this type, in particular with regard to their simplification. It is also an object of the invention to improve the appearance of this coating, in particular to improve the optical properties of the carrier provided with such a coating.

The essence of the invention

In particular, the invention relates to a method for sputtering a coating with photocatalytic properties containing titanium dioxide at least partially crystallized in the form of anatase on a transparent or semi-transparent support. The essence of the invention consists in performing spraying on a carrier under an application pressure of at least equal to 2 Pa. This application pressure is preferably at most 6.67 Pa and in particular at least 2.67 Pa.

As can be seen from said patent document WO 97/10 186, said type of coating can indeed be applied by sputtering. It is a vacuum technique which, in particular, makes it possible to very finely adjust the thickness and stoichiometry of the applied layers. In order to increase the deposition efficiency, this technique is also performed in the presence of a magnetic field. It can also be a reactive technique: it is based essentially on a metal target, which in this case is titanium (or an alloy with another metal or silicon), and the sputtering is carried out in an oxidizing atmosphere, which is generally formed by an Ar / O ₂ mixture. The sputtering can also be non-reactive, starting from a so-called ceramic target which is already in the oxidized form of titanium (or alloy).

- 1 CZ 305963 B6

However, the layers obtained by this type of coating technique are generally amorphous, while the functionality of the coating according to the invention is directly linked to the requirement that the coating must be substantially crystalline. This is why, as is explicitly required in the said patent document, it is necessary to convert the coating to a crystalline form (or to increase its degree of crystallization) by subjecting the coating to heat treatment, for example by heating for about 30 minutes and several hours at a temperature of at least 400 ° C.

In the context of the invention, it has been shown that elevated pressure also has a favorable effect on the crystallization of the coating and its density and roughness, which have a significant effect on the photocatalytic properties of the coating. In some cases, annealing of the coating may optionally be performed. By way of illustration, the generally used deposition pressures for metal oxides are generally in the range from 0.27 to 1.07 Pa, which means that deposition pressures which are quite unusual in this field are used in the context of the invention.

It has also been shown within the scope of the invention that it is possible to omit the post-application treatment step, or at least to make it possible (and / or to limit its time or temperature) by spraying the coating onto a warm carrier and thus not onto a carrier having ambient temperature, namely to a support having a temperature of at least 100 ° C. This heating of the support during application can be performed alternatively or cumulatively using the above-mentioned elevated pressure.

This heating has at least five of the following advantages:

- energy gain achieved during production,

- the possibility of using carriers incapable of withstanding heat treatment at temperatures of 400 or 500 ° C without decomposition,

- in case the annealing requires to place a barrier layer 25 between the support and the photocatalytic coating preventing the diffusion of the support elements (alkaline type in the case of glass), it is possible to use a thinner barrier layer or to omit this barrier layer completely, the processing according to the invention is much less aggressive than annealing,

- much shorter production cycle (because the heat treatment of the support is much shorter and is carried out at a significantly lower temperature),

- omission of storage of "semi-finished products" before annealing.

However, even in this case, a degree of photocatalytic efficiency of the coatings is achieved which is completely identical to the degree of photocatalytic efficiency of the applied and then annealed coating.

The findings made in the context of the invention were not foreseeable in advance since prolonged annealing could be expected to be necessary for the gradual growth of nuclei in the amorphous oxide matrix. This was not the case: hot application favorably affects the application of the coating directly at least partially crystallized.

It was also not expected that the coating thus applied "hot" would preferably crystallize in the form of anatase and not in the form of rutile (the anatase form is much more photocatalytic than the rutile or broockite form of titanium dioxide).

There are several different variants in carrying out the invention, in particular with regard to the type of spray device 45 available. In this way, the support can be heated outside the vacuum chamber before the coating is applied. It is also possible to heat the carrier during application if the application chamber is equipped with heating means. The heating of the carrier can thus be carried out before and / or during the spraying of the coating. The heating may also be gradual during application and may extend only a portion of the thickness of the applied coating (e.g. the top portion).

Preferably, the carrier has a temperature of between 150 and 350 ° C, preferably at least 200 ° C and in particular between 210 and 280 ° C during the application of the coating. Surprisingly, it is thus possible to obtain a sufficiently crystalline coating without having to heat the support to the temperatures generally used in annealing, which are at least 400 to 500 ° C.

-2CZ 305963 B6

In general, when the coating is substantially based on titanium dioxide (TiO ₂ ) and when the coating is applied by sputtering ("hot" or at ambient temperature), the coating has a fairly high refractive index, i.e. higher than 2 or up to 2, 1 or up to 2.15 or 2.2. In general, this refractive index is between 2.15 and 2.35 or between 2.35 and 2.50 (it may be slightly substoichiometric), in particular between 2.40 and 2.45. This is a rather specific characteristic of this type of coating, as coatings of the same character applied by different techniques, such as sol-gel, tend to have much higher porosity and significantly less refractive index (less than 2 and even less than 1.8 or 1.7 ). The invention makes it possible to obtain cathodic spray coatings which have a porosity and / or a roughness (in particular an RMS roughness between 2.5 and 10 nm) which enhances its photocatalytic properties. As a result, the coating can have a refractive index of about 2.15 or 2.35, which is a lower refractive index than that usually achieved with sputtering, which is also indirect evidence of the porosity of the coating. This is an advantage in the optical sense, since the coating with a lower refractive index has a less reflective character at a given thickness.

It has been observed that the crystallographic structure of the coatings is affected by the fact that they are applied cold and then annealed or that they are applied hot. Thus, the coatings applied "hot" and / or at elevated pressure according to the invention unexpectedly have a mean crystallite size of titanium dioxide of less than or equal to 50 nm or 40 nm or 30 nm or between 20 and 40 nm. Coatings applied in a standard manner, especially "cold" and subsequently annealed, tend to have a higher crystallite size, i.e. at least 30 nm or 40 nm and generally between 40 and 50 nm when standard application pressures are used.

In contrast, in one variant of the invention, if the coating is applied at ambient temperature but at elevated pressure and then the coating is annealed, a smaller crystallite size (20 to 40 nm) is obtained which is comparable to the crystallite size of the coatings applied. hot, whether at high or low pressure.

The photocatalytic efficiency of coatings applied at ambient temperature and high pressure and then annealed is much better than the photocatalytic efficiency of coatings applied at ambient temperature and high pressure and then annealed. However, it is certain that the application pressure affects the quality of the applied coating, especially in the case of "cold" application, in a significant way.

Simultaneous heating as the coating grows causes the formation of a microstructure favorable for roughness and / or porosity, which in turn favorably affects the photocatalytic properties. This is somewhat the same as when increased application pressure is used (for example, when applying "cold" followed by annealing).

Thanks to the method according to the invention (hot and / or high pressure application) it is possible to obtain coatings having a RMS (Root Mean Square) roughness measured by a microscope with atomic resolution when performing measurements on the same surface using 2 micrometer steps: - at least 2 nm, in particular at least 2.5 nm, preferably between 2.8 nm and 4.6, in the case of application at ambient temperature and elevated pressure according to the invention (2 to 5 Pa) and subsequent annealing,

at least 4 nm, in particular at least 5 nm, preferably between 5.5 and 6.0 nm, in the case of hot application (about 250 ° C) and without annealing, whether at high or low pressure.

For comparison, the roughness of coatings applied at ambient temperature and standard pressure (especially 0.2 Pa) and then annealed is at best only 2 nm: this proves that the use of elevated pressure makes it possible to achieve a surprisingly high roughness of sputter coatings. , which results in improved photocatalytic properties of the coating.

Preferably, the coating has a geometric thickness of less than 150 nm, in particular having a thickness between 80 and 120 nm or between 10 and 25 nm. It has been shown that even a very thin coating can have sufficient photocatalytic properties (at least for some applications) and, in addition, an optical advantage in that the coating is not very reflective.

-3 CZ 305963 B6

As mentioned above, the sputtering of the coating can be reactive or non-reactive. In both cases, the spray target can be doped in particular with at least one metal. It may be one or more metals selected from the group consisting of Nb, Ta, Fe, Bi, Co, Ni, Cu, Ru, Ce, Mo and Al.

Prior to and / or after this application of the application according to the invention, one or more steps of applying another thin layer or other thin layers, in particular layers having optical, antistatic, antireflective, hydrophilic or protective properties or a degree of increasing the roughness of the coating with photocatalytic properties. It has thus been observed that it may be advantageous to apply (at least) one layer in such a way that it is particularly coarse, for example by pyrolysis or sol-gel technique, and only then to apply a photocatalytic coating. In this case, the photocatalytic coating will tend to "follow" the roughness of the substrate layer, as a result of which this photocatalytic coating will also have a significant roughness, while the cathodic sputter coatings have a rather low roughness. Thus, for example, a substrate layer (with an RMS roughness of at least 5 or 10 nm) of the SIO ₂ , SiOC or SiON type applied by gas phase pyrolysis (CDV) can be formed initially and a photocatalytic coating can be applied to this layer by cathodic sputtering.

Thus, the invention includes any combination between sputtering one or more layers (and thus at least a photocatalytic coating) and applying the substrate or layers by a technique involving thermal decomposition, in particular pyrolysis (liquid phase, gas phase or powder phase), and the sol technique. -gel.

As mentioned above, photocatalytic titanium dioxide coatings have an increased refractive index. This means that they are reflective and therefore the carriers also give a reflective appearance, which is often considered to be a little aesthetic. In addition, the color of reflection can be undesirable in itself, even when accepting gloss. It is not at all easy to improve this aspect of reflection, as the photocatalytic function presupposes an obligatory requirement: the photocatalytic coating must generally be in contact with the external atmosphere in order to absorb ultraviolet radiation and decompose external dirt. Thus, it is not possible to cover this photocatalytic coating with a low refractive index layer (unless it is very thin and / or porous). The photocatalytic coating must also have the minimum thickness necessary to be sufficiently effective.

Thus, another object of the invention was to improve the reflective appearance of the support without disturbing the photocatalytic efficiency of the coating, if possible by reducing its light reflection and / or influencing the reflection color of the support to be as neutral as possible.

The invention therefore also relates to a transparent or semi-transparent support of the glass, glass-ceramic or plastic type, provided on at least part of one of its sides with a coating with photocatalytic properties comprising at least partially crystallized titanium dioxide, in particular crystallized in the form of anatase and obtained by the process of the present invention photocatalytic properties has an RMS roughness between 2.5 and 4.6 nm. According to the invention, this photocatalytic coating is considered to be part of an array of thin anti-reflective layers, the photocatalytic coating being the last layer (i.e. the layer furthest from the support). Said antireflective array is formed by alternating layers with a high and a low refractive index and is in this case terminated by a photocatalytic layer with a high refractive index. The term "anti-reflective" is used here in the context of simplification: in general, this term is used when the effort to achieve light reflection is lower than the light reflection that the carrier itself would have. However, the invention is more concerned with limiting the increase in light reflection (and / or modifying or attenuating the color of the reflection) caused by the use of a photocatalytic coating containing titanium dioxide.

In the context of the invention, the term "layer" means a single layer or several layers arranged one on top of the other. If there are several layers arranged one on top of the other, then the total thickness of this arrangement is equal to the sum of the thicknesses of the individual layers and the total refractive index is equal to the average value of the set of refractive indices of the individual layers. This also applies to the photocatalytic

-4GB 305963 B6 coating. This photocatalytic coating can be combined with some other layer with a high refractive index.

In the context of the invention and as already mentioned above, the term "anti-reflective" means a function which makes it possible to reduce the light reflection value of the coated support and / or to weaken the reflective color, in particular to make it as dull, neutral as possible and as aesthetic as possible. (there is also talk of a "bleaching" effect in this context.

It is a fairly loose and unexpected adaptation of conventional anti-reflective assemblies. In fact, high and low refractive index layers alternate in these assemblies in a known manner, and these assemblies are terminated by low refractive index layers (with a refractive index as close as possible to the refractive index of air equal to 1), these assemblies being formed by layers based on, for example, silica SiO ₂ or magnesium fluoride. However, in this case, the assembly is terminated by a layer with a high refractive index, which is quite paradoxical. Nevertheless, by appropriate selection of the characteristics of the individual layers, such a specific antireflective assembly can achieve a significant attenuation of the reflective character inherent in titanium dioxide with a high refractive index and give the carrier an acceptable reflective color (neutral color in pale shades without red and other warm colors, which are considered for a little aesthetic, especially a neutral color in gray, blue or especially green).

Preferably, the photocatalytic coating has a refractive index higher than 2.30, in particular between 2.35 and 2.50 or between 2.40 and 2.45 (as already mentioned above, the photocatalytic coating can be applied in such a way that the refractive index has only 2 , 10 to 2.30). This photocatalytic coating is preferably applied by sputtering. Its optical thickness, together with the thicknesses of the other layers of the assembly, is chosen so as to achieve a reduction in the light reflection of the carrier. It has been found that the optimal optical thickness is preferably around λ / 2, where λ is equal to 580 nm. This corresponds to an optical thickness between 250 and 350 nm, in particular between 270 and 310 nm; and a geometric thickness between 80 and 120 nm, in particular between 90 and 110 nm. This range of geometric thickness has also been shown to be sufficient to achieve a photocatalytic efficiency that is considered sufficient (photocatalytic efficiency actually depends on numerous parameters, including in particular surface roughness, crystalline layer morphology and layer porosity). It is also possible to use significantly thinner layers, which in particular have a geometric thickness of between 10 and 25 nm.

Depending on whether the photocatalytic coating is applied by "hot" cathodic spraying or at ambient temperature and then annealed, it contains crystallites of various sizes, as mentioned above (generally crystallites less than 30 nm in "hot" deposition and crystallites of about 30 nm). up to 50 nm or more when applied at ambient temperature and standard pressure).

The anti-reflective assembly according to the invention, in its simplest embodiment, comprises three layers and is successively formed by a high refractive index layer, a low refractive index layer and then a high refractive index photocatalytic coating.

The layer or layers of this high refractive index assembly in addition to the photocatalytic coating generally have a refractive index of at least 1.9, in particular between 1.9 and 2.3 or between 1.9 and 2.2. These can be zinc oxide, tin oxide, zirconia or aluminum nitride or silicon nitride. It can also be a mixture of at least two of these compounds.

The optical thickness of these high refractive index layers must be chosen in a suitable manner. Their preferred optical thickness is preferably around λ / 10 at λ equal to 580 nm. This corresponds to an optical thickness between 48 and 68 nm, in particular between 53 and 63 nm, and a geometric thickness between 20 and 40 nm, in particular between 25 and 35 nm. It is also possible to choose a smaller thickness, in particular a thickness between 20 and 48 nm.

The layer or layers with a low refractive index generally have a refractive index between 1.4 and 1.75, in particular between 1.45 and 1.65. These layers can be formed, for example, by silica, alumina

-5GB 305963 B6 or mixtures of these two oxides. Also the optical thickness of these layers with a low refractive index must be chosen appropriately: their optimal optical thickness is preferably around λ / 20 at λ equal to 580 nm. This corresponds to an optical thickness between 20 and 79 nm, in particular between 19 and 39 nm, in particular between 25 and 35 nm, and a geometric thickness between 12 and 50 nm, in particular between 15 and 30 nm, for example between 20 and 28 nm.

In another variant, in the above three-layer assembly, the high refractive index layer / low refractive index layer sequence can be replaced by a layer with an "intermediate" refractive index, i.e. preferably with a refractive index higher than 1.65 and lower than 1.9. The preferred range of refractive index is between 1.75 and 1.85. This layer can be based on silicon oxynitride and / or aluminum. This layer may also be based on a mixture of a low refractive index oxide, such as silica, and at least one higher refractive index oxide, such as tin dioxide, zinc oxide, zirconia and titanium dioxide (the ratio between the individual oxides allows regulate the refractive index of the layer).

This intermediate refractive index layer can also be used as a replacement for the first high refractive index / low refractive index layer sequence of an assembly containing not only three layers but, for example, five or seven layers.

The choice of the optical thickness of this layer with an intermediate refractive index must be chosen in a suitable manner. The optimal optical thickness is around λ / 4 at λ close to 580 nm. This corresponds to an optical thickness between 120 and 150 nm, in particular between 125 and 135 nm, and a geometric thickness between 65 and 80 nm, in particular between 68 and 76 nm.

As mentioned above, these different choices of optical thicknesses take into account the overall reflective appearance of the carrier: there is not only an effort to reduce the value of light reflection (reflection) R _L , but also an effort to give the carrier a shade that is currently considered aesthetic ( which means cool colors rather than yellow or red) and which is as intense as possible. It is therefore necessary to find the best compromise to achieve the best possible overall reflective appearance of the carrier. Depending on the use of the support, it may be advantageous to reduce the value or rather to select a specific reflective color (e.g. quantified by the values a * and b * of the colorimetric system L, a *, b * or the value of the dominant wavelength associated with color purity).

Advantageously, the set of layers of the anti-reflective assembly can be applied in layers by cathodic spraying on one and the same production line.

In an optional variant of the invention, a barrier layer may be inserted between the support and the anti-reflective assembly to prevent diffusion of components from the support. These are especially alkalis when the support is glass. This barrier layer can be, for example, based on silicon oxide (or oxycarbide); silica can be deposited by sputtering, while silicon oxycarbide SiOC can be deposited in a manner known per se by gas phase pyrolysis (CVD). This barrier layer may advantageously have a thickness of at least 50 nm, for example in the range between 80 and 200 nm. Selected from this type of material with a relatively low refractive index (close to 1.45 to 1.55), this layer is generally "neutral" in the optical sense. The silica may contain minor elements which are selected, in particular from the group consisting of Al, C and N.

The invention also relates to glass, in particular single glass (rigid carrier), laminated glass, multi-pane glass of the double glass type, which comprises at least one carrier coated in the manner described above.

Said glass preferably has, due to the anti-reflective effect according to the invention, a light reflection R _L which remains at most equal to 20%, in particular at most equal to 18%. Preferably, this light reflection has a pleasant blue or green hue with negative values of a * and b * in the colorimetric system (L, a *, b *) and in particular lower than 3 or 2.5 in absolute values. This shade has such a pale, pleasing to the eye and low-intensity coloration.

-6GB 305963 B6

Said glass may also contain one or more other functional coatings (applied by sputtering or parolysis or sol-gel technique), either on the same side of the support on which the photocatalytic coating is applied, or on the other side of the support, or on the side of the second support. associated with the first support (double glazing or laminated glass). It is also possible to have a double glass / gas gap / glass with a photocatalytic coating on the outer sides of the glasses and with an assembly of one or two silver layers on the inner sides of the glasses (facing the gas gap). The same type of configuration applies to laminated glass.

The further functional coating or other functional coatings may be, in particular, a non-soiling coating, a sunscreen coating, a low-emission coating, a heating coating, a hydrophobic coating, a hydrophilic coating, an anti-reflective coating, an antistatic coating and another photocatalytic coating. Mention may be made, in particular, of sunscreen or low-emission assemblies with one or more silver or nickel / chromium layers or with titanium or zirconium nitride layers. In the case of metal nitride-based layers, the CVD technique can be used.

In the following part of the description, the invention will be described in more detail by means of examples of its specific embodiment, these examples being of an illustrative nature only and in no way limiting the scope of the invention, which is clearly defined by the definitions and claims.

Example 1 and Comparative Example 1 relate to the hot deposition of photocatalytic titanium dioxide layers by sputtering.

Examples of embodiments of the invention

Example 1

A first layer of SiOC by 80D thickness is applied to a 4 mm thick silicon calcium glass, then a second layer of 90 nm thick photocatalytic titanium dioxide (the SiOC layer can also be replaced by a SiO ₂ : Al layer obtained by reactive sputtering from an Al doped silicon target). ).

The titanium dioxide layer was deposited by sputtering in a magnetic field. It is a reactive sputtering of a titanium target in the presence of oxygen. The glass is preheated to a temperature of about 220 to 250 ° C. This temperature is kept constant during the sputtering of the layer by means of a heating device located next to the target.

The titanium dioxide layer obtained has a refractive index of 2.44. It is crystallized in the form of anatase (it may also contain amorphous zones) with a mean crystallite size of less than 25 nm.

Its photocatalytic activity was quantified by a palmitic acid test; in this test, palmitic acid of a given thickness is applied to the photocatalytic surface and the photocatalytic surface is exposed to ultraviolet radiation at a wavelength of about 365 nm at a surface intensity of about 50 W / m ² throughout the test, after which the disappearance rate is determined. palmitic acid according to the following relationship:

V (nm.h ') = [palmitic acid thickness (nm)] / [2 xt _1/2 disappearance (h)].

For the layer according to the invention, the photocatalytic efficiency is determined by calculation to be at least 10 nm.h -1, in particular the catalytic efficiency between 20 and 100 nm.h ^-1 , depending on the choice of the pressure and temperature parameters of the deposition.

_{Depending on the illuminant D 6, the} glass coated in this way has a light reflection of 23% and a reflection value of a * and b * of about 17 and 28, respectively, according to the colorimetric system (L, a *, b *).

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The photocatalytic efficiency of said coating is thus satisfactory, but its optical appearance is still purely reflective in nature and too intensely reflective in color.

It should be noted that it is possible to increase the photocatalytic efficiency of the coating by subjecting the coating to conventional annealing (for one or several hours at a temperature of at least 400 ° C) after application of the coating.

Comparative Example 1

The procedure of Example 1 was repeated, but this time the titanium dioxide layer was applied to an unheated support and then treated by annealing at 500-550 ° C for several hours. In addition, the silica support layer is only up to 100 nm thick. The morphology of the layer is somewhat different and contains crystallites with a size rather larger than 30 nm.

The photocatalytic efficiency of the coating is the same as the photocatalytic efficiency of the layer of Example 1 without annealing, but is lower if a smaller thickness of the silica support layer is chosen.

This fact thus confirms that the hot coating according to the invention, which makes it possible to "save" the subsequent often long annealing operation, is not at the expense of the photocatalytic efficiency of the coating. This also confirms the secondary advantage achieved by the invention: when applied by heat and eliminating subsequent annealing, a thinner barrier layer can be used while achieving the same catalytic efficiency (thus shortening the production time and reducing the costs associated with the production of said product).

Example 2 and the following examples relate to the incorporation of a photocatalytic layer of titanium dioxide with a high refractive index, in particular applied by sputtering, into an antireflection assembly in order to improve the optical properties.

Example 2 (implementation)

A set of the following layers is applied to 4 mm thick silicate calcium glass:

glass / Si ₃ N ₄ ⁽¹⁾ / SiO ⁽²⁾ / TiO ⁽³⁾ nm 22 nm 104 nm (geometric thickness).

Layer (1) Si ₃ N ₄ is deposited by reactive cathodic sputtering in the presence of nitrogen from an Al-doped silicon target.

_{The SiO 2} layer (2) is deposited by reactive cathodic sputtering in the presence of oxygen from an Al-doped silicon target.

Layer (3) TiO ₂ is photocatalytic and was applied hot as described in Example 1.

Between the glass and the Si ₃ N ₄ layer, it is optionally possible to insert a layer of silica with a thickness of about 100 nm obtained in the same way as the silica layer (2) described above. This layer has almost no effect on the optical properties of the support and can serve as a barrier layer for alkali transition from glass. This layer is all the more possible because the layers of the anti-reflective coating below the photocatalytic layer, i.e. layers (1) and (2), themselves constitute quite sufficient barrier layers in addition to their optical properties; these two layers already form a 100nm barrier for components capable of diffusing from the glass.

The photocatalytic efficiency of layer (3) is 80 nm.h '.

-8CZ 305963 B6

Alternatively, it is possible to use a TiO ₂ layer applied cold and then annealed in the manner described in Comparative Example 1.

On the reflective side of the layers, the following result is achieved for such an assembly:

R ₁ (according to illuminant D ₆ s): 17.3%, a * (R 1) = -2, b * (R _L ) = -2.8,

Xd (nm) = 494 nm (dominant wavelength of light reflection).

pe (%) = 2.5% (purity of reflective paint).

It can be seen that with respect to Example 1, a lower pale blue-green reflective color is obtained _{here at a lower R L value.} Overall, the glass has a significantly improved aesthetic appearance.

Example 3

This example is very close to Example 2, the only change being the slightly changed thickness of the TiO ₂ layer. In this case it is a report:

glass / Si ₃ N ₄ ⁽¹⁾ / SiO ₂ ^<2) / TiO ⁽³⁾ nm 22 nm 99 nm (geometric thickness).

The following result of the light reflection is obtained (with the same meanings of the stated quantities):

R1 = 17.9%, a * = -0.8, b * = 0.7,

Λ _d (nm) = 494 nm, pe (%) = 0.8%.

There is thus achieved a slightly different compromise at a slightly higher value of R _l and lower absolute values of a * and b *.

Example 4 (modeling)

This example is very close to Example 2 with the only change concerning the change in the thickness of the first Si ₃ N ₄ layer:

glass / Si ₃ N ₄ ⁽¹⁾ / SiO ₂ ⁽²⁾ / TiO ⁽³⁾ nm 22 nm 104 nm (geometric thickness).

The following result of the light reflection is obtained (with the same meanings of the stated quantities):

R1 = 15.8%, a * = 0, b * = -9,

_{Λ d} (nm) = 475 nm, pe (%) = 4.9.

In this case, the value of R1 is significantly reduced, and the reflective color has changed hue.

-9CZ 305963 B6

Example 5 (modeling / comparative)

In this case, compared to Example 2, all layer thicknesses are changed. It is an assembly: glass / Si ₃ N ₄ ^(l) / SiO ₂ ⁽²⁾ / TiO ⁽³⁾ nm 30 nm 75 nm (geometric thickness).

The following result of the light reflection is obtained (with the same meanings of the stated quantities):

R1 = a * = b * = Xd (nm) = pe (%) = 25.8%, -0.8, 0.7, 492 nm, 0.5%.

In contrast, if the support has a satisfactory reflective color, it has an R _L value significantly higher than 20%, which is too high; therefore, the changed thicknesses are not optimal.

Example 6 (modeling / comparative)

In this example, the layer thicknesses differ even more from the thicknesses determined by the invention, and are the following:

glass / Si ₃ N ₄ ^(l) / SiO ₂ ^<2) / TiO ⁽³⁾ nm 20 nm 60 nm (geometric thickness).

The following result of the light reflection is obtained (with the same meanings of the stated quantities):

R1 = a * = b * = X _d (nm) = pe (%) = 30%, -2.3, 7.2, 587 nm, 14%.

In this case, the value of R1 is too high and even the reflective color is not very desirable and too intense.

The appearance of the carrier is therefore not satisfactory.

Example 7 (implementation)

This time it is the following set:

glass / SnO ₂ ⁽¹⁾ / SiO ^{2 (2)} / TiO ^{2 (3)} nm 27 nm 105 nm (geometric thicknesses).

In this case, the Si ₃ N ₄ layer was replaced by a SnO ₂ layer deposited by reactive cathodic sputtering in the presence of oxygen from a tin target.

The following result of the light reflection is obtained (with the same meanings of the stated quantities):

R1 = a * = b * = λ _d (nm) = pe (%) = 17.4%, -2.8, -2.7, 496 nm, 2.8%.

-10GB 305963 B6

The reflective appearance of the support is close to the reflective appearance of the support obtained in Example 2.

Example 8 (isation model)

In this case, the first two layers are replaced by a single layer of silicon oxynitride SiON having a refractive index of 1.84. It is therefore a report:

glass / SiON / TiO ₂ nm 101 nm (geometric thickness).

The following result of the light reflection is obtained (with the same meanings of the stated quantities):

R1 = a * = b * = X _d (nm) = pe (%) = 17.4%, 0, -1.08, 480 nm, 1%.

The reflective appearance of the carrier is therefore satisfactory.

Example 9 (modeling)

In this case, Example 8 is repeated with the difference that the refractive index of the SiON layer is 1.86. A slightly modified reflective appearance is achieved:

Rl 17.8%, a * = -1.1, b * = -1.5, Λ _d (nm) = 494 nm, pe (%) = 1.3%.

Example 10 (implementation)

In this case, it is a report:

glass / Si ₃ N ₄ / SiO ₂ / Si 3 N 4 / TiO ₂ ⁽³⁾ nm 17.5 nm 24 nm 92.5 nm (geometric thickness)

The last layer with a high refractive index is thus a superposition of the Si ₃ N ₄ and TiO ₂ layer. The light reflection R1 on the layer side is between 16.5 and 17.5%. The photocatalytic efficiency is around 80 nm.h “ ¹ .

Example 11 (implementation)

This example returns to the type of assembly shown in Example 3, in which, however, different thicknesses of the individual layers are used. This is a report:

glass / Si ₃ N ₄ ^(l V SiO ₂ ⁽²⁾ / TiO ^<3)

14.5 nm 43 nm 14.4 nm.

The light reflection on the layer side is between 13 and 16%. The changes in optical properties when each of the assembly layers changes by 3% are as follows:

- 11 CZ 305963 B6

AR _L :

Aa *:

From *:

0.8%, 0.3, 1.3.

In this example, a photocatalytic activity of about 15 to 20 nm.h ¹ is achieved.

This example is interesting for several reasons: it is not very sensitive to changes in layer thickness and the assembly will therefore be easy to manufacture industrially. The assembly remains sufficiently photocatalytic, even if the titanium dioxide layer is very thin. This consists also satisfactory from a colorimetric point of view.

In conclusion, the invention provides a new method of vacuum deposition of layers containing photocatalytic T102. The invention also provides a new type of anti-reflective / decolorizing assembly which is terminated by a high refractive index layer, an assembly which is easy to manufacture industrially and significantly weakens the reflective appearance of Tio ₂ without compromising the photocatalytic properties. The invention makes it possible to obtain glasses with a pale blue or pale green reflection, while maintaining the thicknesses of the photocatalytic layer of the order of hundreds of nanometers. It is also possible to choose a significantly thinner photocatalytic layer, i.e. a layer having a thickness of 12 to 30 nm.

Both objects of the invention (product and method) can be used in the same way for photocatalytic coatings which contain only T1O2.

The invention therefore proposes the "hot" application of these coatings and alternatively the application of these coatings at ambient temperature and their respective subsequent heat treatment, preferably with specific application pressure control, to obtain vacuum applied layers having completely unusual characteristics exhibiting the remarkable non-soiling properties layers.

Claims (35)

A process for applying a coating with photocatalytic properties comprising at least partially crystallized titanium dioxide, in particular crystallized in the form of anatase, by sputtering on a transparent or semi-transparent glass, glass-ceramic and plastic type support, characterized in that the sputtering is carried out at a deposition pressure P of at least 2. Bye. Method according to Claim 1, characterized in that the application pressure P is at most 6.67 Pa and in particular at least 2.67 Pa. Method according to one of the preceding claims, characterized in that the sputtering is carried out on a support heated to a temperature of at least 100 ° C. Method according to claim 3, characterized in that the substrate is heated before and / or during the sputtering and / or during at least part of the sputtering. Process according to Claim 3 or Claim 4, characterized in that the support has a temperature of between 150 and 350 ° C during sputtering, preferably a temperature of at least 200 ° C, in particular a temperature of between 210 and 280 ° C. -12CZ 305963 B6 Process according to Claim 1 or Claim 2, characterized in that the sputtering is carried out at ambient temperature, the annealing-type heat treatment optionally being carried out after the coating has been applied. Method according to one of the preceding claims, characterized in that the coating has a refractive index higher than 2, in particular higher than 2.1, preferably between 2.15 and 2.35 or between 2.35 and 2.50. Process according to one of the preceding claims, characterized in that the coating comprises titanium dioxide crystals having a size less than or equal to 50 or 40 nm, preferably between 15 and 30 nm or between 20 and 40 nm. Method according to one of the preceding claims, characterized in that the coating has an RMS roughness of at least 2 nm, in particular at most 10 nm, preferably between 2.5 and 7 nm or between 2.8 and 5 nm. Method according to one of the preceding claims, characterized in that the coating has a geometric thickness of less than 150 nm, in particular between 80 and 120 nm or between 10 and 25 nm. Method according to one of the preceding claims, characterized in that a reactive cathodic sputtering from a substantially metal target or a non-reactive cathodic sputtering from a ceramic target is carried out. Method according to Claim 11, characterized in that the target from which the sputtering is carried out is doped with a metal, in particular selected from the group consisting of Nb, Ta, Fe, Bi, Co, Ni, Cu, Ru, Ce, Mo and Al . Method according to one of the preceding claims, characterized in that it is followed by and / or followed by at least one thin layer having an optical, antistatic, decolorizing, antireflective, hydrophilic or protective function or a function of increasing the roughness of the coating with photocatalytic properties, a sputtering technique or a technique involving thermal decomposition of the pyrolysis type or a sol-gel technique. Method according to Claim 13, characterized in that at least one thin layer is applied before it by pyrolysis, in particular by CVD, this layer having an RMS roughness of at least 5 nm, in particular at least 10 nm. Transparent or semi-transparent carrier of the glass, glass-ceramic or plastic type, provided on at least part of one of its sides with a coating with photocatalytic properties comprising at least partially crystallized titanium dioxide, in particular crystallized in the form of anatase and obtained according to one of the preceding claims, characterized in that the coating having photocatalytic properties has an RMS roughness between 2.5 and 4.6 nm. 16. A transparent or semi-transparent support of the glass, glass-ceramic or plastic type, provided on at least part of one of its sides with a coating with photocatalytic properties containing at least partially crystallized titanium dioxide, in particular crystallized in the form of anatase, said coating having an RMS roughness between 2.5 and 4. , 6 nm and a high refractive index of at least 2 and at most 2.45, forming the last layer of an assembly of thin "anti-reflective" layers, said assembly consisting of alternating layers of high and low refractive index, characterized in that each of the low refractive index layers have a refractive index between 1.40 and 1.75 and a geometric thickness between 12 and 50 nm, and in that each of the high refractive index layers, except for the photocatalytic coating, has a refractive index between 1.9 and 2, 3. Support according to Claim 16, characterized in that the coating with photocatalytic properties has a refractive index equal to or higher than 2.30, or equal to or lower than 2.30, in particular between 2.15 and 2.25. - 13 CZ 305963 B6 Carrier according to Claim 16 or 17, characterized in that that the coating with photocatalytic properties has an optical thickness between 200 and 350 nm, in particular between 210 and 310 nm. Support according to Claim 16 or 17, characterized in that the coating with photocatalytic properties has an optical thickness of less than 50 nm, in particular between 25 and 45 nm. Support according to Claim 16 or 17, characterized in that the coating with photocatalytic properties has a geometric thickness of between 80 and 120 nm, preferably between 90 and 110 nm or between 10 and 25 nm. Support according to one of Claims 16 to 20, characterized in that the coating with photocatalytic properties comprises titanium dioxide crystallites which are less than or equal to 50 or 40 nm, in particular between 15 and 30 nm or between 20 and 40 nm, or crystallites titanium dioxide having a size of at least 30 nm, in particular between 30 and 50 nm. Support according to one of Claims 16 to 21, characterized in that the antireflective multilayer assembly comprises at least three layers, which are successively a first layer with a high refractive index, a second layer with a low refractive index and a coating with photocatalytic properties, optionally combined with at least one further layer with a high refractive index. Support according to one of Claims 16 to 22, characterized in that the layer or layers with a high refractive index have a refractive index of between 1.9 and 2.2. Support according to Claim 24, characterized in that the layer (s) are based on tin oxide, zinc oxide, zirconia, aluminum nitride or silicon nitride or on a mixture of at least two of these compounds. Support according to Claim 22 or Claim 23, characterized in that the first layer with a high refractive index has an optical thickness of between 48 and 68 nm, in particular between 53 and 63 nm, or between 20 and 48 nm. The carrier according to claim 22 or claim 23, characterized in that the first layer with a high refractive index has a geometric thickness between 20 and 40 nm, or between 25 and 35 nm, or between 10 and 20 nm. Support according to one of Claims 16 to 26, characterized in that the layer or layers with a low refractive index have a refractive index of between 1.45 and 1.55, and are, for example, based on silica, alumina or a mixture of both. of these oxides. Support according to one of Claims 16 to 27, characterized in that the low refractive index layer has an optical thickness of between 20 and 79 nm. Support according to one of Claims 16 to 28, characterized in that the low refractive index layer has a geometric thickness of between 15 and 30 nm. Support according to any one of claims 16 to 29, characterized in that a barrier layer is inserted between said support and the anti-reflective assembly, preventing the diffusion of alkali metal-type components from the support. Support according to Claim 30, characterized in that the barrier layer is a silica-based layer optionally containing Al, C or N, in particular with a thickness of at least 50 nm, for example between 60 or 80 nm and 200 nm. - 14GB 305963 B6 32. Glass, in particular single glass; laminated glass or multi-pane glass of the double-glazed type, characterized in that it comprises at least one support according to one of Claims 15 to 31. Glass according to Claim 32, characterized in that it has a light reflection R ₁ of at most 20%, in particular at most 18%, on the layer side. Glass according to Claim 32 or 33, characterized in that it has a light reflection in blue or green on the layer side with negative values of a * and b * in the colorimetric system (L, a *, b *), which are preferably in absolute values lower than 3 or 2.5. Glass according to Claim 32, characterized in that it also comprises at least one further functional coating, in particular a non-soiling, sunscreen, low-emissivity, heating, hydrophobic, hydrophilic, antireflective or antistatic coating, or a second coating with photocatalytic properties.